Quality control of the hottest Gravure plastic fil

2022-08-15
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Quality control of Gravure plastic film 2

in order to meet the needs of overprint, such as small lines and words can't be overprinted in multiple colors, and there can't be small anti white words on the overprint pattern, and it should not be left blank on the overprint pattern and covered with other small words. For the version with strict overprint requirements for portraits, try not to separate other color versions from black, blue, red and yellow versions. For printing, the bar code should be arranged as the line direction is consistent with the circumferential direction of the cylinder. In terms of color assurance, if conditions permit, it is best to make plates separately for the large field background color and the hierarchical pattern version, and try to use a special version for the large field background color. The two color jump areas of 80% and 5% must be fully considered for hanging, and the limit of gradient hanging time point should be more than 10%

② ink blending

adjust the adaptability of ink printing, such as the viscosity and concentration of ink. The principle is to adjust the viscosity of ink and adjust it with diluent (solvent). Before printing, determine the viscosity of ink according to the situation of plate roller and machine table. During the printing process, add solvent often according to the volatilization of solvent, but do not overdo it, and try to ensure that the viscosity of ink remains unchanged; When ink is to be diluted, diluent (ink blending oil) must be used. Do not dilute it with solvent

allocation of ink color. In this regard, we need to pay attention to the following points: the light source for observing the color should be the standard light source (D65). If there is no standard light source, it is better to be in the direction of the North window with sunshine. When preparing spot color, primary color ink should be selected for blending. The primary color ink mentioned here refers to the ink directly produced by the ink factory with pigments. The brightness and saturation of such ink can be guaranteed. Use as few ink colors as possible to cause corrosion of sheet metal for color matching. The more the number of colors, the greater the color matching error, and the greater the difficulty of re color matching

3. Proofing

when a set of printing plates is printed, a standard sample must be confirmed first. Some manufacturers take the proofing draft of the plate making factory as the standard sample, and the sample cannot be matched at the time of final printing and delivery. Therefore, the printer must be used for proofing before printing, and it will be used as the standard sample after being confirmed by the customer or relevant personnel. The printing of standard samples should be carried out under normal printing process conditions, otherwise it will be very difficult to trace samples in the future printing, so the following points should be paid attention to when proofing:

① the process bar company indicates that the most basic printing process conditions should be selected

② try to choose a lower ink viscosity

③ the primary color ink should be proofed after adding a certain amount of diluent. Try to use as little as possible, especially the contaminated ink that has been used for many times, to proofing from scratch

④ it is absolutely forbidden to do all non-standard operations in order to excessively pursue the effect during proofing, such as increasing the concentration and viscosity to increase the hue, adjusting the pressure, scraper to improve the ink transfer rate, etc

⑤ the ink must be stirred evenly before use, especially the spot color ink

⑥ the spot color ink prepared by yourself must be scraped and accurately recorded for filing, which can be used as a reference for future deployment

⑦ try to achieve the normal printing speed when proofing

⑧ if conditions permit, after confirming the basic color of the sample, first print a certain number of products (such as a roll of film), and then take samples to confirm as standard samples, which are sealed and stored as archives

⑨ after the confirmation of the standard sample, the connected 2 ~ 3M should be cut as the equivalent standard sample, which should be properly stored in a place without heat source and ultraviolet light. In the future, the cut part should be used as the printing sample during each printing

4. Common troubleshooting

① dirty version: in plastic gravure printing, the non printing surface of the drum is often adhered with hazy, in which the mined organic graphite is stripped to a thin layer of resin (with pigment in the resin), which produces fewer layers, and is transferred to the substrate as sheet dirt or linear dirt, which is called dirty version. The generation of dirty version is not only related to the soft hardness of the scraper, the pressure of the scraper, the contact angle of the scraper and the quality of the version cylinder, but also related to the viscosity of the ink. (to be continued)

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